CVE-2018-20865 in cPanel
Summary
by MITRE
cPanel before 76.0.8 has Self XSS in the WHM Additional Backup Destination field (SEC-459).
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Analysis
by VulDB Data Team • 07/15/2020
The vulnerability identified as CVE-2018-20865 represents a self-cross-site scripting flaw within cPanel software versions prior to 76.0.8, specifically affecting the WHM Additional Backup Destination field. This issue falls under the category of client-side vulnerabilities that can be exploited by malicious actors to execute arbitrary code within the context of a user's browser session. The vulnerability was classified as SEC-459 by cPanel's security team, highlighting its potential impact on system integrity and user security.
The technical flaw manifests in how the WHM interface handles input validation for the Additional Backup Destination field, where user-supplied data is not properly sanitized before being rendered back to the browser. This allows an attacker who has access to the WHM interface to inject malicious scripts that will execute in the context of the logged-in administrator's session. The vulnerability is particularly concerning because it operates within the WHM administrative interface, which typically grants users elevated privileges and access to critical system functions. The flaw stems from insufficient input sanitization and output encoding practices that fail to properly escape special characters and script tags in user-provided data.
The operational impact of this vulnerability extends beyond simple script execution, as it can potentially allow attackers to escalate privileges and gain unauthorized access to sensitive system information. An attacker could leverage this vulnerability to steal session cookies, modify backup configurations, or even inject malicious code that persists across system operations. The self-XSS nature means that the malicious payload is executed within the victim's own browser session, making detection more challenging and potentially allowing for prolonged exploitation. This vulnerability directly aligns with CWE-79, which defines Cross-Site Scripting as a common weakness in web applications, and can be mapped to ATT&CK technique T1059.007 for Scripting, where adversaries use scripting languages to execute malicious code.
Mitigation strategies for CVE-2018-20865 primarily focus on upgrading to cPanel version 76.0.8 or later, which includes proper input validation and output encoding fixes for the affected field. Organizations should also implement additional security measures such as regular security audits of administrative interfaces, monitoring for suspicious backup configuration changes, and ensuring that only authorized personnel have access to WHM administrative functions. Network segmentation and multi-factor authentication can provide additional defense-in-depth layers to protect against exploitation attempts. The vulnerability demonstrates the critical importance of input validation in administrative interfaces, as these areas typically handle the most sensitive operations and represent prime targets for attackers seeking to gain system control. Security teams should also consider implementing web application firewalls to detect and block suspicious script injection attempts in real-time.